1
Adjust rack to top position (top and middle positions for 4 servings) and preheat oven to 425 degrees. Wash and dry produce.
Dice potatoes into ½-inch pieces. Cut broccoli florets into bite-size pieces if necessary. Halve, peel, and mince half the onion (whole onion for 4). Zest and quarter lemon.
Trim and discard woody bottom ends from asparagus; cut crosswise into 1-inch pieces. (Save potatoes for another use.)